问题

I need to transfer a MongoDB query to a different system. For this reason I would like to use the MongoDB Extended JSON. I need this to be done mostly because I use date comparisons in my queries.

So, the kernel of the problem is that I need to transfer a MongoDB query that has been generated in a node.js back-end to another back-end written in Go language.

Intuitively, the most obvious format for sending this query via REST, is JSON. But, MongoDB queries are not exactly JSON, but BSON, which contains special constructs for dates.

So, the idea is to convert the queries into JSON using MongoDB Extended JSON as form of representation of the special constructs. After some tests it's clear that these queries do not work. Both the MongoDB shell and queries sent via node.js's need the special ISODate or new Date constructs.

Finally, the actual question: are there functions to encode/decode from JSON to BSON, taking into account MongoDB Extended JSON, both in JavaScript (node.js) and Go language?

Updates

Node.js encoding package

Apparently there is a node.js package that parses and stringifies BSON/JSON. So, half of my problem is resolved. I wonder if there is something like this in Go language.

Sample query

For example, the following query is in normal BSON:

{ Tmin: { $gt: ISODate("2006-01-01T23:00:00.000Z") } }

Translated into MongoDB Extended JSON, it becomes:

{ "Tmin": { "$gt" : { "$date" : 1136156400000 }}}

回答1:

After some research I found the mejson library, however it's for Marshaling only, so I decided to write an Unmarshaller.

Behold ejson (I wrote it), right now it's a very simple ejson -> bson converter, there's no bson -> ejson yet, you can use mejson for that.

An example:

const j = `{"_id":{"$oid":"53c2ab5e4291b17b666d742a"},"last_seen_at":{"$date":1405266782008},"display_name":{"$undefined":true},
"ref":{"$ref":"col2", "$id":"53c2ab5e4291b17b666d742b"}}`

type TestS struct {
    Id          bson.ObjectId `bson:"_id"`
    LastSeenAt  *time.Time    `bson:"last_seen_at"`
    DisplayName *string       `bson:"display_name,omitempty"`
    Ref         mgo.DBRef     `bson:"ref"`
}

func main() {
    var ts TestS
    if err := ejson.Unmarshal([]byte(j), &ts); err != nil {
        panic(err)
    }
    fmt.Printf("%+v\n", ts)

    //or to convert the ejson to bson.M

    var m map[string]interface{}
    if err := json.Unmarshal([]byte(j), &m); err != nil {
        t.Fatal(err)
    }
    err := ejson.Normalize(m)
    if err != nil {
        panic(err)
    }
    fmt.Printf("%+v\n", m)

}

来源：https://stackoverflow.com/questions/25218061/sending-a-mongodb-query-to-a-different-system-converting-to-json-and-then-decod

标签

json